Present damage-risk limits for exposure to intermittent noise are based on inadequate data and are therefore unrealistic. On the one hand, use of the total-immission principle being actively promoted both on a national and international scale is generally over-conservative, since this principle assumes that the temporal pattern of noise exposure is irrelevant (only the total energy matters) and thus ignores the ability of the auditory mechanism to recuperate between noise bursts. On the other hand, damage-risk contours proposed by CHABA, based on a criterion of certain limiting temporary threshold shift (TTS) 2 minutes after cessation of the daily noise exposure, are not only complicated and unwieldy but are under-conservative due to faulty generalizations and unjustified extrapolations involved in their preparation. This research will provide empirical data that will permit correction and simplification of the CHABA contours. Normal listeners will be exposed for 8 hours to various patterns of interrupted noise, and the TTS produced will be measured at intervals from 2 minutes to 16 hours following exposure. Noise-exposure parameters to be varied include octave-band frequency and level, rate of interruption, and noise burst duration. The effects of (1) Moderate noise during "quiet" periods, (2) The presence of pure-tone components in the noise, and (3) Irregular (multi-level) patterns will also be studied. One or more general TTS-based damage-risk criteria will be suggested, and equal-risk contours for intermittent noise will be constructed for each criterion.